Recently, there has been significant growth in the use of standardized tests to certify new public school teachers. The policy objective that motivates teacher testing, as with other worker screening devices, is to identify and hire those most qualified to teach. Do state certification tests fulfill their intended goal of improving the quality of teachers in public schools?

Educators, policymakers, and economists all agree that better teachers are the foundation for building better public schools.

The Carnegie Task Force on Education, in its 1986 report and a 1996 follow-up report, called for the introduction of more centralized systems of certification for public school teachers. Stricter and more centralized teacher licensing also has been supported by the National Education Association and a range of groups promoting education reform. Proposed licensing systems involve accreditation programs, longer apprenticeships, and teacher testing.

The discussion on teacher testing presumes that testing is of great value in predicting teacher quality, a view supported by the National Council for Accreditation of Teacher Education.

In practice, designing effective testing strategies is difficult since standardized tests are not the most accurate predictors of an applicant's future performance. Test requirements may establish a minimum achievement standard, but certification requirements also may discourage high-quality applicants from choosing to teach in the public schools. Stricter certification requirements may be seen as costly hurdles by experienced teachers or teachers with attractive employment opportunities in other fields.

From an economic point of view, occupational licensing serves as a measure of worker quality and helps to maintain standards when additional information about quality is unavailable. These mandatory licensing requirements impose a barrier to occupational entry that is likely to increase wages in the licensed occupation.

So far, the natural economic solution for attracting better teachers has been to raise teacher pay. From 1960 to 1998, teacher salaries rose in real terms by 43 percent, outpacing the increase in non-teacher salaries. At the same time, however, the IQ scores of those teachers fell.

In the recent study, "Does Teacher Testing Raise Teacher Quality? Evidence from State Certification Requirements," University of Chicago Graduate School of Business professor Jonathan Guryan and Joshua D. Angrist of Massachusetts Institute of Technology estimate the impact of the most basic component of teacher licensing provisions-the requirement that teachers pass a certification test that can be seen as similar to medical boards or legal bar exams.

Guryan and Angrist find that state-mandated teacher testing increases teacher wages with no corresponding increase in teacher quality. Their results suggest that the tests as currently written are not an effective way to improve the quality of new public school teachers.

"Testing public school teachers is not a silver bullet that can improve teacher quality," says Guryan.

The History of Teacher Testing

Testing of public school teachers is not a new phenomenon. In many states, teachers were tested in basic subjects beginning in the 19th century. In the early part of the 20th century, a number of states began more widespread use of testing for certification. World War II led to a decrease in the pool of potential teachers, and a subsequent increase in the hiring of teachers with alternative certification. As a result, most states discontinued the use of teacher testing by the end of WWII.

Beginning in the 1960s, some states began testing prospective teachers in an effort to ensure teachers meet minimum standards for basic skills and subject knowledge. By 1999, 43 states required applicants to pass a standardized certification test. The most commonly used tests are the National Teacher Examination and the Pre-Professional Skills Test published by the Education Testing Service; the latter is commonly known as the "Praxis" exam.

Different states have different testing regulations, and there is no single standardized test. States pick which test or combination of tests they require based on the particular type of license a teacher is seeking. States also determine the minimum cut-off test score for obtaining a license.

Screening for Quality

To study the effect of teacher testing on wages and teacher quality, Guryan and Angrist used data from the Teacher Demand and Shortage Survey (TDSS), a component of the Schools and Staffing Survey (SASS), which links information on school districts, teachers, and students. The first round of SASS was the 1987-88 school year, followed by rounds in 1990-91, 1993-94, and 1999-2000. In addition to providing information on teacher salaries in each survey period (except 1990-91), SASS includes measures of teacher educational background that Guryan and Angrist use as a measure of teacher quality. Each round of the survey includes almost 5,000 districts, and a typical district has 3,000 pupils and 160 teachers.

The authors combined teacher responses to the survey to provide district-level measures of teacher characteristics and quality, such as the proportion of teachers with state certification. The authors accounted for commonly used teacher quality measures such as the average SAT score at the teacher's undergraduate college, obtained from the Higher Education Research Institute. Finally, the authors collected information on testing requirements in different states for each survey year. The authors also asked district administrators about their use of basic skills and subject tests.

Measuring teacher wages was fairly straightforward, since most schools have a system that determines salaries for every teacher in the district, usually based on their educational background and experience.

The authors find that state testing requirements are associated with slightly higher wages. The salaries of teachers with a BA degree are about 2.4 percent higher in states that require a test of basic skills. Subject test requirements also appear to be associated with higher wages. State testing requirements are associated with higher wages for teachers with an MA, and for experienced teachers with an MA.

Guryan and Angrist's findings are in keeping with the notion that certification requirements establish barriers to entry that subsequently increase teacher salaries. Restricting the entry of potential teachers via testing requirements increases the bargaining power of teacher's unions and allows them to negotiate for higher wages.

To measure teacher quality, the authors used the average SAT scores of the teacher's undergraduate institution. The authors do not find a clear association between testing requirements and the quality of the teacher's undergraduate institution as measured by average SAT scores. Testing does not lead schools to hire teachers who attended more selective colleges, nor does testing increase the likelihood that teachers will teach material they studied in college or graduate school.

"Tests are not perfect measures of the skills necessary to be a good teacher," says Guryan. "To the extent that the tests are flawed, many people who would have been very good teachers may fail. The worse the test is written, the worse this problem will be. Testing can actually be counter productive in this sense, and lead schools to hire worse teachers."

Looking Ahead

Even though salaries tend to be higher in public schools, bureaucratic and costly certification requirements may send the best teachers to private schools. The notion that these requirements limit teacher supply or adversely affect teacher quality is behind current education reforms promoting "alternative certification" paths for public school teachers.

Concerns about testing notwithstanding, the question remains how best to improve the quality of the public sector teacher labor force. The authors suggest that using the SAT scores of applicants' undergraduate institutions might be a useful screening tool that may also force school districts to focus more on teacher quality. For example, public school principals could use a potential teacher's SAT score as another piece of information in the hiring process.

"Public schools should have as much information about their teaching applicants as possible, and to the extent that SAT scores are a good predictor of teaching ability, schools should use the scores," says Guryan. "However, it is not a good idea to force all public schools to adhere to one rule about how to hire teachers."

Even if testing currently functions more as a barrier than as a quality screen, Guryan notes that testing could still be useful for gauging the quality of applicants. To make the testing system more useful would however require that the cut-off test scores for certification be much higher. The tests themselves would also have to be more informative about the skills that make someone a good teacher. To write a test that would accomplish all these goals would be a difficult or potentially impossible task.

"If there was a test that was so challenging that only the brightest people would pass it, the problem would then be increasing teacher salaries to convince those people to be teachers and not pursue other job opportunities," says Guryan.

Currently, public school teacher salaries are quite rigidly set and not as closely tied to performance and ability, which is not necessarily beneficial for a talented new teacher. Salaries are based on seniority, education, and the school system in which the teacher works. Guryan argues that teacher pay should be changed to reflect teacher ability and performance.

"If you want to attract the best and brightest to teaching, then teacher salaries will have to be higher," says Guryan. "Besides that, we should remove impediments to the teacher labor market rather than impose them."

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Jonathan Guryan is associate professor of economics at the University of Chicago Graduate School of Business.